Thursday, October 11, 2018

Thursday Afternoon Update: A Quick, Rainy Visit from Now-Tropical Storm Michael (UPDATED)

**Updated 4:32 pm 10/12/2018: See bottom of entry.**

GOES 16 GEOCOLOR (true daylight color) looped image 1422 -1852 UTC Oct 10, 2018

Unfortunately, this looped animation includes a gap of an hour to 90 minutes that results in a distinct (and unwanted) "jump" in the image.

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Well, I had intended to post an entry last night discussing Hurricane Michael, but I didn't get around to it. About Hurricane Michael, "he" made landfall on the Florida panhandle yesterday at Mexico Beach / Tyndall AFB afternoon around 1:30 pm EDT with 155mph maximum sustained and a central minimum pressure of 919 mb.

Tallahassee NWS (EVX) radar in standard composite mode looped 1:05 pm - 1:42 pm Oct 10, 2018 as Hurricane Matthew made landfall.

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This made Michael the strongest U.S. landfalling hurricane in terms of wind since Andrew in 1992, the third strongest in terms of low pressure (after Camille in 1969 and the 1935 Labor Day hurricane) and, possibly, the fourth strongest in terms of wind (though I'm certain on that one).

Mexico Beach, Fla., was completely destroyed, as was much of Panama City, Fla. So far, the death toll is put at 6, and given the extent of destruction, the name is being retired from the NHC roster.

NECONUS composite radar mosaic looped 1808 - 1918 UTC

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While I will write more about Hurricane Michael, for this entry, I just want to make it a short mid-afternoon update to note that the heavy rainfall from the remnants of the tropical cyclone -- still a tropical storm as it races northeastward with its center (as of 2 pm EDT) near Greensboro, N.C. -- is on the doorstep of the Metro D.C. area, although I'm not convinced that D.C. itself will see much in the way of rainfall owing to how the system is moving.

The Baltimore / Washington (Sterling) NWS Forecast Office (LWX) county warning area (CWA) weather advisories with legend updated 3:33 pm EDT Oct 11, 2018

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Rainfall amounts of about 1 inch are expected in the immediate D.C. area -- maybe even a bit less, looking at the radar trends -- but more like 2 to 4 inches across the Tidewater and lower Eastern Shore and into parts of New Jersey.

The NWS Wakefield (AKQ) CWA weather advisories with legend as of 3:49 pm EDT Oct 11, 2018

I don't think I've ever seen so many warnings in effect in a single CWA. And the colors resemble one of those Crayola boxes of 120 crayons. Speaking of weather advisories, yesterday there was the very rare "extreme wind warning" in effect for the places at and near Michael's landfall for winds to 130 mph. Yikes.

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The system is already transitioning to an extratropical (non-tropical) one that will literally rocket across the Atlantic Ocean as it gets caught up in the strengthening westerlies -- with the system to the British Isles by Monday / Tuesday.

The Raleigh NWSFO (RAH) CWA weather advisories with legend updated 3:50 pm EDT Oct 11, 2018

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In that sense, the system will be very "progressive" and won't be anything like a negatively tilted nor'easter. However, it is forecasted to intensify as it pushes into the western Atlantic. Right now, we are deep inside a tropical air mass with dew points around the Baltimore/Washington region of 73F to 75F range, which is ridiculous for mid-October, but in keeping with the relentless humidity and warmth of this year.

Sterling (LWX) NWS radar in standard base mode reflectivity looped 3:02 pm - 3:43 pm Oct 11, 2018

The way the precipitation is moving on this radar doesn't really impress me in terms of it "washing" (pun intended) into the immediate Washington, D.C. area. What's more, looking outside, it hardly looks like a major storm is approaching. Yes, it is overcast above D.C. and local environs, but it is a flattened, dull gray, middle-level type of overcast (i.e., altostratus clouds). It wouldn't shock me if we really miss out here.

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Wakefield (AKQ) NWS radar in standard base mode reflectivity looped 3:02 pm - 3:47 pm EDT Oct 11, 2018

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On the topic of warmth (and, implicitly, humidity), today's 83F high at KDCA marked the 136th time this year that it was 80F or higher there and thus officially in Washington, D.C. -- thus tying the 136 days set in 1970 and 2007. (The first 80F this year was the ridiculous 82F on Feb 21st.) However, today might be the last of the 80F+ days for 2018.

Raleigh (RAX) NWS radar in standard base mode reflectivity looped 3:06 pm - 3:53 pm EDT Oct 11, 2018

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To that point, the good news is that as the hurricane exits -- transitioning quickly to a powerful extratropical (non-tropical) low that rockets across the Atlantic in the westerlies to the British Isles by Monday/Tuesday -- a strong cold front will push through that marks the beginning of a major pattern change. Oh, yes, the 0.13" of rainfall that fell earlier today pushed KDCA to exactly 50 inches of precipitation for the year-to-date.

NHC 5-day track and infographic for Tropical Storm Michael, advisory 20A, Oct 11, 2018

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OK, I'm signing off now. My intention is to post another entry tonight. Given that I'm flat broke until tomorrow, I'm quite sure I'll be home and just watching TV. As I went to the gym the past two nights, I'm not going to go again tonight.

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UPDATED 4:32 pm EDT 10/12/2018

Sterling (LWX) NWS radar in standard base mode reflectivity looped 8:12 pm - 8:52 pm EDT Oct 11, 2018

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Rainfall amounts yesterday from the remnants of Hurricane Michael were as follows for the three major airport ASOS climate stations:

KDCA: 1.51"
KIAD: 0.95"
KBWI: 0.77"

Sterling (LWX) NWS radar in standard composite mode looped 8:01 pm - 8:41 pm EDT Oct 11, 2018

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The radar presentation at times last night -- especially the composite mode -- looked really impressive even over the immediate D.C. area, but the heaviest rainfall was, not unexpectedly, over portions of southern Maryland and central and eastern Virginia where there were widespread amounts of 3 to 6 inches of rain recorded.

Regional NWS radar mosaic for a portion of the eastern United States looped 8:15 pm - 9:00 pm EDT Oct 11, 2018, as prettied up and displayed by Weather Underground.

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Yesterday's rainfall increased the big yearly surpluses and puts Baltimore (KBWI) within shot of it third-ever 60-plus inch year along with 1889 (62.35") and 2003 (62.66").

The yearly totals and departures for each are:

KDCA: 51.34" +20.01"
KIAD: 51.58" +18.49"
KBWI: 55.41" +22.29"

As of now -- with 80 days to go in calendar year 2018 -- KIAD is at its 6th wettest year ever (with full year records back to 1964). For KDCA, with a much longer base period stretching back to 1871, it is at its 13th wettest. It's worth pointing out that 8 of those are in the pre-airport period (i.e., 1871 - mid-1945).

As for KBWI, it is at its 8th wettest. It too has a pre-airport period stretching from 1871 - May 1950, but most of these wetter years are in the airport period.

I'll post more detailed numbers later this month to capture monthly, seasonal, and yearly amounts and departures.

NWS high-resolution surface weather map for a portion of the eastern United States at 21Z Oct 11, 2018

This shows Tropical Storm Michael transitioning quickly into an extratropical low as it accelerated along a sharp cold frontal boundary marking a major weather pattern change for the eastern U.S.

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The weather today is wonderfully shockingly different -- air temps around 65F but dew points around 42F or a full 30F below yesterday's ridiculous values. There is also a lovely, cool northwesterly breeze.

End of update and of entry.

--Regulus

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